Research On Spectral Line Narrowing Technology For Two-cavity Dual-frequency All-solid-state Laser

All solid-state lasers have good stability,small size and long life,which are widely used in laser radar,coherent detection and laser interference ranging.In the process of synthetic wave absolute distance interferometry,where the dual-frequency all-solid-state laser is used as the light source,the laser linewidth determines the coherence length,which affects the ranging range.To achieve a wide range of absolute ranging,a narrow linewidth dual-frequency all-solid-state laser is required,which implies that the research on the line narrowing techniques for the dual-frequency all-solid-state laser has important application value.This thesis is mainly focused on the dual-cavity dual-frequency Nd:YAG all-solid-state laser.The external cavity feedback method and technology are adopted,that is,the dual-frequency laser line is narrowed by changing the extra-cavity length and the reflectivity of extra-cavity mirror.The main research contents can be included as follows:Firstly,the research of single-frequency laser line narrowing technology at home and abroad is introduced.The system composition and operating principle of two-cavity dual-frequency Nd:YAG solid-state laser are analyzed.Then two-cavity dual-frequency all-solid-state laser based on plane mirror extra-cavity feedback method is designed.The Nd:YAG all-solid-state laser line narrowing scheme is developed to analyze the spectral linewidth of the dual-frequency Nd:YAG laser by changing the extra-cavity length and the feedback magnitude of the extra-cavity.The feasibility of the laser line narrowing scheme is analyzed theoretically.Secondly,an extra-cavity feedback 1064nm single-frequency Nd:YAG all-solid-state laser system was established.The laser oscillation characteristics,output characteristics and laser linewidth characteristics were experimentally studied,where the laser’s threshold pump power is 1.15W,the slope efficiency is 15%,and the 1064nm single-frequency laser output power is 115mW.When the length of the outer cavity is taken as 50mm,100mm and 150mm,the variation of the laser linewidth is experimentally studied by placing an adjustable attenuator in front of the extra-cavity mirror to change the feedback amount of the extra-cavity.Experiment results show that the spectral linewidth decreases with the increase of the outer cavity length and the extra-cavity feedback amount.The laser line width decreases from 0.087 nm to 0.026 nm,and the corresponding frequency linewidth decreases from 23.055 GHz to 8.74 GHz Thirdly,an external cavity feedback 1064nm dual-cavity dual-frequency Nd:YAG solid-state laser system was established.The laser oscillation characteristics and laser linewidth characteristics of linear cavity and right-angle cavity were experimentally studied.The single-frequency laser output power of linear cavity and right-angle cavity reach82.4mW and 38.5mW,respectively;when the outer cavity lengths of linear cavity and right-angle cavity are 50mm,100mm and 150mm respectively,the amount of feedback of extra-cavity is changed,and the linear cavity is experimentally studied.And straight-angle cavity single-frequency laser line-width varies.The results show that the single-frequency laser linewidth of linear cavity and right-angle cavity decreases with the increase of extra-cavity length and extra-cavity feedback.The single-frequency laser line-width of linear cavity decreases from 0.088nm to 0.027nm.The frequency line-width is reduced from 23.266 GHz to 7.1 GHz;the right-angle cavity single-frequency laser linewidth is reduced from 0.069 nm to 0.028 nm,and the corresponding frequency line-width is reduced from 16.4 GHz to 7.505 GHz.To conclude,this thesis focuses on the theoretical analysis and experimental research of spectral line narrowing for dual-chamber dual-frequency Nd:YAG all-solid-state lasers.The results show that the laser line width varies with the length of the outer cavity and the extra-cavity.This research has laid an important foundation for the further research and development of narrow-line-width dual-frequency all-solid-state lasers.